Apparatus for the thermal treatment of solids

ABSTRACT

Apparatus for the thermal treatment of solids in straighttraveling grates including a working path extending through a sintering machine where grate trucks are passed therethrough at one speed, and a conveying device for carrying the grate units back to the working path at a speed much greater than the work speed. An acceleration device is positioned at the end of the work path and is shaped to transfer a grate truck to the conveying device while at the same time accelerating the truck to the speed of the conveying device. A deceleration device positioned at the end of the conveying device transfers a grate truck to the work path while decelerating it to the work path speed.

United States Patent Inventor Werner Schmidt Frankfurt, Germany Appl.No. 26,989 Filed Apr. 9, 1970 Patented Dec. 28, 1971 Assignee DrnvoCorporation Pittsburgh, Pa. Priority Apr. 18, 1969 Germany P l9 19 668.0

APPARATUS FOR THE THERMAL TREATMENT OF SOLIDS Primary Examiner-John J.Camby Att0rneyParmelee, Utzler & Welsh ABSTRACT: Apparatus for thethermal treatment of solids in straight-traveling grates including aworking path extending through a sintering machine where grate trucksare passed therethrough at one speed, and a conveying device forcarrying the grate units back to the working path at a speed muchgreater than the work speed. An acceleration device is positioned at theend of the work path and is shaped to transfer a grate truck to theconveying device while at the same time accelerating the truck to thespeed of the conveying device A deceleration device positioned at theend of the conveying device transfers a grate truck to the work pathwhile decelerating it to the work path speed.

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WERNER sum/0r W 47 g I A rrarneys APPARATUS FOR THE THERMAL TREATMENT OFSOLIDS The invention relates to an apparatus for the thermal treatmentof solids in straight-traveling grates, where the grate units enteringthe no-load track through deflecting wheels are conducted back to thework path by means of conveyor devices.

For the thermal treatment of solids on traveling grates various systemsare known. The form of construction of these machines chiefly used inthe practice consists of an endless belt of individual grate trucksstrung together, which are charged with the material to be treated atthe loading point of the upper band. During the forward movement of thegrate trucks on the upper band the material is then subjected to athermal treatment. At the end of the upper band, the grate trucks aregripped by the so-called lowering wheel, tilted, emptied, conducted intothe lower band, and at the end thereof seized by a so-called liftingwheel and again conducted onto the upper band. In this arrangementalways more than half of the installed load surface is not utilized forthe treatment process, so that due to the high-manufacturing costs ofthe grate trucks great investment costs per throughput unit arerequired.

Various suggestions have already been made for the better utilization of1 the installed load surface. Thus designs of straight-traveling gratesare known where the lower band of the above-described traveling gratemachines is arranged parallel and at the same level alongside the upperband." After completion of the thermal treatment process on the firstbelt, the grate trucks are emptied by tilting, shifted laterally to thesecond belt, and charged with material. On the second belt there thenoccurs likewise a heat treatment process, which is completed at the endof the second belt. These traveling grate machines, however, haveseveral disadvantages, which interfere with their practical use. Thuseither only an intermittent operation is possible, which must beinterrupted every time a grate truck is tilted, or expensive devices,e.g., means for pulling up the last grate truck before the tiltingoperation, are necessary to permit continuous operation. in addition,complicated shifting devices for the transport of the grate trucks fromone belt to the other belt and an exactly matched control for allmovements are required. Moreover, the trouble proneness due to the manymovable parts and the rough operating conditions is great. The saving ofthe grate trucks of the lower band returning empty is offset by the costof a complex operating system for the second belt.

Forms of construction of the straight traveling grates are also knownwhere the grate trucks are emptied by tilting at the end of the upperband and rotated 180 by special devices, so that they enter the lowerband with the load surface up. On the lower band the grate trucks arethen again charged with the material discharged from the upper band, sothat a heat treatment of the material occurs also on the lower band.After completion of this second heat treatment, the grate trucks areemptied, rotated 180, and returned to the upper band. This type can alsooperate so that the first heat treatment occurs on the lower band andthe second heat treatment on the upper band, it being then necessary toconvey the material into the charging device for the upper band byadequate transport devices. The difficulties in the operation of thesetraveling grates reside mainly in the complicated reversing mechanismsand the necessary capsulation against fouling from the dust raised atthe discharge points. In addition, the discharge must either occurwithin the lowering wheels, and the transfer device for the materialtransport to the lower band must likewise be arranged within thelowering wheel, or additional transport devices are needed.

It has also been proposed to fit only the upper band and the liftingwheel of sintering machines with grate trucks, and to design the lowerband, with the exception of a certain distance before the lifting wheel,only as return path for the emptied grate trucks. The gate trucks arethen guided down onto the lower band at the end of the upper band bymeans of curve tracks. The lower band is arranged sloping down in thedirection of the lifting wheel, so that the grate trucks pass throughthis section freely. This arrangement has the great disadvantage thatthe grate trucks impinge on the grate trucks present before the liftingwheel at considerable speed and are easily damaged. It has also beenproposed to brake the grate trucks at the outlet of the curve tracksharply by a braking device, whereby a better discharging and reductionof the impact was to be achieved, but also with this arrangement theimpingement of the grate trucks is still so strong that damage isinevitable.

The arrangement of a special brake device, operating on the principle ofthe friction wheel, just before the lifting wheel in the lower band didbring a certain improvement, but still suffers from technicalinadequacies.

A method different from the above-cited state of the art for improvingtraveling grates provides passing the grate units, supplied by thelowering wheel to the lower band, to the lifting wheel by means of aconveying device. The return then occurs at a speed which is muchgreater than the speed of the grate units on the working track. Thetransfer of the grate units from the working belt to the no-load trackoccurs preferably with gear wheels which seize the grate units by rollsmounted on the shaft, transporting them so that in the descent they donot touch the preceding or following grate unit. Having arrived on theno-load track, the grate unit is seized by drive pins of a conveyingdevice, e.g., two endless chains running parallel, and are taken alongat a speed about lO-l5 times greater (referred to that of the workingtrack).

Although it is possible by the cited proposal to reduce the totalsurface and hence the total weight of the grate units by about 35percent and to avoid wear of the grate units at their transverse side byimpingement during the descent in the zone of the lowering wheel, itsuffers from considerable. disadvantages. The most important is that thecomparatively slowly lowered grate units are seized by drive pins of theconveying devices running 10 to 15 times faster and are thus exposed tothe effect of forces which do not occur in normal operation. Thereforean unbearably high wear occurs, or else the construction of the grateunits involves an actually unnecessarily high expense.

This invention avoids the above-mentioned disadvantages. It relates toan apparatus for the thermal treatment of solids on straight travelinggrates where the grate units entering the no load track throughdeflecting wheels are guided back from the beginning to the end of theno-load track, with the aid of conveying devices at a much greater speedthan that which they have during the thermal treatment, and ischaracterized by a device which accelerates the grate unit at the end ofthe work belt for transfer to the conveying device from working speed toreturn speed, and a device which decelerates the grate unit at the endof the no-load track for transfer to the work track from return speed towork speed.

The devices for acceleration and deceleration of the speed of the grateunits have preferably the form of levers or else of specially shaped camplates mounted in pairs on a shaft. When using levers, the accelerationor deceleration of the grate units can be achieved in that the rotaryshaft of the levers itself executes an accelerated or deceleratedmovement. Preferably, however, the lever pairs, as well as the camplates, are mounted on a shaft suspended outside the center of circledefined by the deflection path, so that at constant rotary movement ofthe shaft the acceleration or deceleration of the grate units isattained due to the varying circumferential speed of the contact pointsbetween the rolls of the grate units and the levers or cam plates. Inthe apparatus according to the invention for the thermal treatment ofsolids, the upper band of the traveling grate may be designed as workingbelt and the lower band as no-load belt, or the upper band may bedesigned as no-load belt and the lower band as working belt.

Synchronism is provided between the conveying device and the device forthe transfer of the grate units to the working belt. A simplepossibility suitable for this consists in that the conveying device anddevice for the transfer of the grate units are driven by means of thesame assembly and that difierent speeds are brought about by differenttransmission ratios.

Other details and advantages of the invention will become apparent asthe following description of certain present preferred embodimentsthereof proceed.

In the accompanying drawings I have shown certain present preferredembodiments of this invention in which:

FIG. 1 is a side elevation, partly in schematic, ofa traveling gratewhere the work path is arranged in the upper band and the no-load trackin the lower band. Also shown are devices in accordance with the presentinvention for accelerating and decelerating the grate units, suchdevices being shown as specially designed levers.

FIG. 2 is a side elevation view, partly in schematic, of a travelinggrate where the work path is arranged in the lower band and the no-loadtrack in the upper band. Also shown are devices in accordance with thepresent invention for accelerating and decelerating the grate units.

FIG. 3 is a side elevation view, partly in schematic, of a travelinggrate where the work path is arranged in the upper band and the no-loadtrack in the lower band. Also shown are cam devices in accordance withthe present invention for accelerating and decelerating the grate units.

FIG. 4 is a side elevation view, partly in schematic, of a travelinggrate where the work path is arranged in the lower and the no-load trackin the upper band. Also shown are cam devices in accordance with thepresent invention for accelerating and decelerating the grate units.

In the form of construction according to FIG. I, grate trucks 2 traversethe sintering path arranged in the upper band of the sintering machineI. The drive occurs through a driving wheel or wheel pair 3, whichengages in the rolls 4 disposed on the axles of the grate trucks 2. Atthe end of the sintering path, the first grate truck is seized by thedevice 5 designed as a lever, separated from the grate truck chain, andaccelerated on the deflection track 6 from working speed to the speedcorresponding to the conveying device 7. The design of lever 5 and ofthe grate truck axles by rolls 4 is such that an acceleration of thegrate truck beyond the intended speed due to gravitation cannot takeplace. In fact, if the acceleration caused by gravitational forces wouldbe greater than intended, roll 4 of the rear grate truck axle would runup on the flank away from the direction of movement of lever 5 andthereby prevent too great an acceleration of the grate truck. Moreover,the arm of lever 5 may be designed widened toward the pivot, so that atthe point of the deflection track 6 at which the gravitational forceswould cause an acceleration beyond the desired speed the distancebetween front and rear rolls 4 is practically filled by the lever 5 andthus absolute positive conduction of the grate truck exists.

The grate truck, having arrived on the no-load track 8, is seized by thedrive pin 9 at the roll 4 and dragged on the no-load track atpractically constant speed, which may be about lO-l5 times the speed ofthe trucks on the sintering path. At the end thereof, the grate truck istransferred to lever 10, whose circumferential speed at the takeup pointof the grate truck is practically identical with the return speedthereof. On the way leading through the deflecting track 11 back to thesintering path the circumferential speed of the contact point betweenroll 4 of the grate truck and lever 10, and hence the speed of the gratetruck itself, decreases continually, so that it is in the end taken upby the driving wheel 3 at working speed and pressed against thepreceding grate truck chain.

Wheel 12 has a separating function, i.e., it is to prevent that due toinevitable differences in tensile strength of the sinter, two or evenmore grate trucks are pulled off by the lever S at the individualabutment points of the grate trucks. The separating wheel 12 may beunnecessary if, for example, pellets are fired or if the deviceaccording to the invention is applied to processes where large areaintercrescence of the charge is not to be expected. Then, however,provision must be made by suitable measures, e.g., by inclination of thework track, that the cohesion of the individual grate units ispreserved.

The design of the device according to the invention illustrated in FIG.2 differs from that of FIG. I by interchange of the position of the workbelt and of the no-load track. The various shapes, configurations, andparts of the apparatus correspond to those explained in reference toFIG. 1. However, for the device for transferring the grate truck to theconveyor, the form of a fork 10 is advisable.

In the form of construction of the apparatus of the invention accordingto FIG. 3, cam plates 13 and 14, having specially arranged guide strips15 and 16, take over the function of the levers 5 and 10. The use of thecam plates 13 and 14 as devices for the acceleration or deceleration ofthe speed of the grate trucks 2 involves the advantage that the drivewheel 3 (as per FIG. 1 or 2) and the separating wheel (as per FIG. 1 or2) can be dispensed with. Because of the shape of their flanks, the camplates 13 and 14 also take over the driving and separating function.Lastly, for the form of construction here shown only one roll orrespectively one roll pair 4 is required at the front axle of the gratetruck.

In the device according to FIG. 4, the working track is in the lowerband and the no-load track 8 with conveying device 7 in the upper handof the traveling grate. The function of the cam plates 13 and 14corresponds to that described in FIG. 3. In this case the guide strips15 and 16 (as per FIG. 3) are not necessary.

The apparatus according to the invention for the thermal treatment ofsolids is applicable to the sintering of ores and ore concentrates, tothe firing of pellets of any origin, to the calcining of any substances,and to drying and cooling processes.

I claim:

1. Apparatus for use in the thermal treatment of solids comprising:

a work path extending through a treatment zone;

' traveling grate units for carrying solids through the treatment zone;

power means for driving the grate units at one speed along the workpath;

no-load track means for carrying empty units back to the work path at aspeed greater than the work speed;

first elongated revolvable transfer means arranged at the discharge endof the work path for engaging and transferring the grate units from thework path to the no-load track means and for accelerating the units tothe no-load track speed; and

second elongated revolvable transfer means arranged at the feed end ofthe work path for engaging and transferring the grate units from theno-load track means to the work path and for decelerating the units tothe work path speed.

2. Apparatus as set forth in claim 1 wherein said first transfer meansincludes a rotatable lever member arranged at the end portion of thework path and shaped to engage a grate unit to guide same onto theno-load track; and said second transfer means includes a rotatable levermember arranged at the beginning portion of the work path and shaped toengage a grate unit to guide same onto the work path.

3. Apparatus as set forth in claim 1 wherein said first transfer meansincludes a rotatable cam member arranged at the end portion of the workpath and shaped to engage a grate unit to guide same onto the no-loadtrack; and said second transfer means includes a cam member arranged atthe beginning portion of the work path and shaped to engage a grate unitto guide same onto the work path.

4. Apparatus as set forth in claim 1 wherein said work path is arrangedabove said no-load track means.

5. Apparatus as set forth in claim I wherein said no-load track means isarranged above said work path.

6. Apparatus as set forth in claim 3 wherein the cam member of saidsecond transfer means forms said power means by being shaped to drivethe grate units along the work path.

1. Apparatus for use in the thermal treatment of solids comprising: awork path extending through a treatment zone; traveling grate units forcarrying solids through the treatment zone; power means fOr driving thegrate units at one speed along the work path; no-load track means forcarrying empty units back to the work path at a speed greater than thework speed; first elongated revolvable transfer means arranged at thedischarge end of the work path for engaging and transferring the grateunits from the work path to the no-load track means and for acceleratingthe units to the no-load track speed; and second elongated revolvabletransfer means arranged at the feed end of the work path for engagingand transferring the grate units from the no-load track means to thework path and for decelerating the units to the work path speed. 2.Apparatus as set forth in claim 1 wherein said first transfer meansincludes a rotatable lever member arranged at the end portion of thework path and shaped to engage a grate unit to guide same onto theno-load track; and said second transfer means includes a rotatable levermember arranged at the beginning portion of the work path and shaped toengage a grate unit to guide same onto the work path.
 3. Apparatus asset forth in claim 1 wherein said first transfer means includes arotatable cam member arranged at the end portion of the work path andshaped to engage a grate unit to guide same onto the no-load track; andsaid second transfer means includes a cam member arranged at thebeginning portion of the work path and shaped to engage a grate unit toguide same onto the work path.
 4. Apparatus as set forth in claim 1wherein said work path is arranged above said no-load track means. 5.Apparatus as set forth in claim 1 wherein said no-load track means isarranged above said work path.
 6. Apparatus as set forth in claim 3wherein the cam member of said second transfer means forms said powermeans by being shaped to drive the grate units along the work path.